Thanks for running the commands.
That’s indeed very odd.
Also, I’m sorry, but I’m missing the required knowledge of helm and kubernetes which is why I can’t help you further. I’ve tried to help you as far as I could within application context - in your case something seems to be very special (and I can’t figure it out).
Changing the FQDN shouldn’t be an issue at this point. Something’s breaking within your login routine. That shouldn’t happen at all. You could try to create a local account and then login to that. If it happens with your local accounts as well, it seems like something broke during importing.
Again, that’s just a guess. Technically everyone else using helm and similar should have this exact problem then. Earlier this month I’ve been working with docker-compose in combination with upgrading (3.1 to 3.3) with LDAP activated (and living data inside). The only difference to your scenario is that I haven’t removed the data and had a “normal” in place upgrade.
If a in place upgrade is no option within helm, I can’t tell why and how to solve this issue. I’m sorry.
Sorry, but this is a english only board.
Reason for this is that we want to help as many of our users as possible. If someone else has e.g. your problem, he’ll be able to find the solution (if there’s any). Switching to german would help very little people and would technically be similar to fullfilling a service contract.
I hope you can understand this. 
Maybe @anon29869905 can help you on this if he wants spare time.
Above error messages might sound familiar to him - if we’re lucky I’m even wrong.